are crocodiles or birds closer to dinosaurs

Introduction

The evolutionary relationship between birds, crocodiles, and dinosaurs has been a subject of extensive research and debate. Understanding which of these groups is closer to dinosaurs involves examining various anatomical, physiological, and behavioral traits.

Key Insights

Common Ancestry and Evolutionary Pathways:
- Birds are widely accepted to have evolved from theropod dinosaurs, a group of bipedal saurischian dinosaurs.
- Some researchers argue that birds and crocodiles share a common pseudosuchian origin, independent of dinosaurs.
Physiological and Anatomical Similarities:
- Birds and crocodiles share several physiological traits, such as similar amino acids in β-keratins, oviduct homologies, and similar forelimb structures.
- Both birds and crocodiles have a functional gizzard containing swallowed stones and a mechanism to prevent indigestible residues from passing into the intestine, which is not found in unquestionable theropod groups.
Behavioral Traits:
- Core reproductive behaviors, such as nest construction and parental care, are universal among modern crocodilians and may reflect primitive characters for archosaurs, including dinosaurs.
- The presence of integumentary sense organs (ISOs) in crocodilians, which are used during courtship and parental care, suggests that similar structures in dinosaurs may have had similar functions.

Conclusion

Birds are generally considered closer to dinosaurs, specifically theropod dinosaurs, based on extensive anatomical and physiological evidence. However, crocodiles share several significant physiological and behavioral traits with both birds and dinosaurs, indicating a complex evolutionary relationship. While birds are more directly descended from theropod dinosaurs, crocodiles also share a common archosaur ancestry with both groups.

Are crocodiles or birds closer to dinosaurs

Summary

Introduction

Key Insights

Conclusion

Sources and full results

New look at the origin of birds and crocodiles

Birds and crocodiles share a common pseudosuchian origin, independent of dinosaurs, with otic region features supporting this hypothesis.

Crocodilian behaviour: a window to dinosaur behaviour?

Modern crocodilians and birds share physiological similarities, suggesting that similar complex behaviors, including parental care, may have been present in dinosaurs.

Comparative digestive physiology of archosaurs with notes on bird origins

Birds and crocodiles share similar digestive physiology, suggesting a possible ancient split between avian and dinosaur lineages.

The Ancestry of Birds

Birds and crocodiles are likely to be more closely related than previously realized, but the evidence does not support a common thecodont ancestor.

Cranial anatomy of Stenonychosaurus inequalis (Saurischia, Theropoda) and its bearing on the origin of birds

Stenonychosaurus inequalis' skull anatomy suggests small carnivorous dinosaurs are more plausible bird ancestors than pseudosuchians or crocodiles.

Spinosaurs as Crocodile Mimics

This new spinosaur variety has skull features similar to crocodiles, suggesting it may have been adapted for eating fish rather than terrestrial animals.

Crocodiles as dinosaurs: behavioural thermoregulation in very large ectotherms leads to high and stable body temperatures

Crocodiles, like dinosaurs, maintain high and stable body temperatures through behavioral thermoregulation, with access to shade or water being crucial for survival in low latitudes.

Three crocodilian genomes reveal ancestral patterns of evolution among archosaurs

The ancestral archosaur genome shows extremely low base substitution rates, possibly due to a consistently longer generation time over evolutionary history.

The complete mitochondrial genome of Alligator mississippiensis and the separation between recent archosauria (birds and crocodiles).

The complete mitochondrial genome of Alligator mississippiensis suggests that the divergence between avian and crocodilian lineages occurred at approximately equal to 254 million years ago, challenging the Haemothermia hypothesis.

Linnean Society of London

Owen later challenged), he also believed that dinosaurs were closely related to modern birds.

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